Coating compositions containing reactive diluents and methods

ABSTRACT

The present invention provides coating compositions that include reactive diluents and have high performance, low VOC levels, and low irritation levels. Certain embodiments of the present invention include water and water-dispersible polymers and other embodiments do not include water.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 60/478,070, filed on Jun. 12, 2003, which isincorporated herein by reference in its entirety.

BACKGROUND

There is a significant need for lower VOC-containing (volatile organiccompound-containing) systems in the coatings industry due to increasingenvironmental restrictions. Typically, lower VOC-containing systems havebeen achieved by using lower molecular weight polymers. However, thiscan result in products having poorer performance.

In an effort to reduce the amount of VOC's released, and maintainperformance, manufacturers have been using water-based polyurethanes.Such water-based polyurethanes are usually linear polymers and producefilms that have chemical resistance lower than the highly crosslinkedfilms of solvent-borne urethane systems. Preparing the polyurethanecoating compositions by pre-crosslinking a water-based polyurethanepolymer can be accomplished by incorporating a large amount of monomersthat have more than two reactive functional groups in the prepolymerstage. However, this results in highly viscous prepolymer blends thatcannot be easily dispersed in water. Diluents have been used to addressthis problem of viscosity, but many are highly irritating either toskin, eyes, or both. In many instances the presence of an “irritating”diluent will require that extensive industrial hygiene measures beundertaken before using the product. However, such measures may not bepractical and such products may not be selected as a result.

Thus, what is needed are coating compositions that have highperformance, low VOC levels, and low irritation levels.

SUMMARY

The present invention provides coating compositions that includereactive diluents and have high performance, low VOC levels, and lowirritation levels. Certain embodiments of the present invention includewater and water-dispersible polymers and other embodiments do notinclude water.

Preferred water-dispersed coating compositions include no more thanseven weight percent (wt-%) (more preferably no more than 4 wt-%)volatile organic compounds (VOC). However, certain other compositions,e.g., alkyd-based compositions, may contain higher VOC levels.

In one embodiment, a coating composition is provided that includes: awater-dispersible polymer (e.g., polyurethanes, epoxies, polyamides,chlorinated polyolefins, acrylics, oil-modified polymers, polyesters,and mixtures or copolymers thereof); a reactive diluent that includes acompound having a molecular weight of at least 350 grams/mole(preferably a molecular weight of 350 grams/mole to 1000 grams/mole),wherein the reactive diluent is substantially free of ethylene oxide andpropylene oxide moieties and has an OH-functionality of no more than 30milliequivalents KOH/gram; and water.

In another embodiment, a coating composition is provided that includes awater-dispersible polymer, a substantially non-irritating reactivediluent, and water. If the reactive diluent is provided as a mixture ofcompounds, the mixture as a whole is substantially non-irritating. Thatis, the phrase “reactive diluent” can encompass one or more compounds.If it is a mixture of compounds, the entire mixture must besubstantially nonirritating.

In another embodiment, a coating composition is provided that includesan oil-modified polymer (e.g., an alkyd, an oil-modified polyurethane,oil-modified epoxy, oil-modified polyamide, oil-modified acrylics, andmixtures or copolymers thereof); and a reactive diluent that includes acompound having a molecular weight of at least 350 grams/mole(preferably a molecular weight of 350 grams/mole to 1000 grams/mole),wherein the reactive diluent is substantially free of ethylene oxide andpropylene oxide moieties and has an OH-functionality of no more than 30milliequivalents KOH/gram. The oil-modified polymer is water-dispersiblefor certain embodiments.

In another embodiment, a coating composition is provided that includesan oil-modified polymer and a substantially non-irritating reactivediluent. If the reactive diluent is provided as a mixture of compounds,the entire mixture is substantially non-irritating.

Typically, the water-dispersible polymer includes amine or acidfunctionality. It can also include ethylenic unsaturation (e.g.,(meth)acrylate functionality or auto-oxidative carbon-carbon doublebonds).

The reactive diluent can include a (meth)acrylate (wherein“(meth)acrylate” refers to an acrylate and a methacrylate), a vinylether, a (meth)allyl ether (wherein (meth)allyl ether refers to an allylether and a methallyl ether), or mixtures or copolymers thereof.Preferably, the reactive diluent includes a (meth)acrylate-functionalcompound, such as those selected from the group consisting ofdi-(trimethylolpropane tetraacrylate), di-(trimethylolpropanetetramethacrylate), and mixtures thereof.

The present invention also provides methods for coating that involveapplying a coating composition to a substrate and allowing the coatingcomposition to harden. The present invention also provides coatingsprepared or preparable from the coating compositions described herein.For example, a coating of the present invention is preparable by amethod that involves applying a coating composition of the presentinvention to a substrate and allowing the coating composition to harden.

The present invention also provides a method of preparing a coatingcomposition, the method involves: providing a mixture that includes awater-dispersible polymer and a reactive diluent having a viscositybelow 100,000 centipoise (cps) at processing or use temperatures,wherein the reactive diluent has a molecular weight of at least 350grains/mole and is substantially free of ethylene oxide and propyleneoxide moieties and has an OH-functionality of no more than 30milliequivalents KOH/gram; and dispersing the mixture in water.Significantly, because of the use of the reactive diluent, this processdoes not require the need for added solvent.

As used herein, a “reactive diluent” includes one or more relatively lowmolecular weight compounds that react with at least one of thefollowing: a polymer (e.g., a water-dispersible polymer such as apolyurethane), itself, another reactive diluent, or any combination ofthese; a reactive diluent can form an interpenetrating network with thepolymer or can crosslink with the polymer; and can be a monomer,oligomer, or polymer.

Also herein, “water-dispersible” means the polymer is itself capable ofbeing dispersed into water (i.e., without requiring the use of aseparate surfactant) or water can be added to the polymer to form astable dispersion (i.e., the dispersion should have at least one monthshelf stability at normal storage temperatures).

Also herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.).

Also herein, the terms “comprises” and variations thereof do not have alimiting meaning where these terms appear in the description and claims.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Coating compositions of the present invention include a reactive diluentand either a water-dispersible polymer or an oil-modified polymer, whichcan be water-dispersible or not. When combined with the polymer, thereactive diluent is capable of providing a low VOC-containingcomposition.

Preferably, coating compositions of the present invention have aviscosity below 100,000 cps, more preferably below 30,000 cps, even morepreferably below 15,000 cps, even more preferably below 5,000 cps, andmost preferably below 1,000 cps at processing or use conditions.

Preferably, the coating compositions include no more than 7 weightpercent (wt-%) volatile organic compounds. More preferably, the coatingcompositions of the present invention include no more than 4 wt-%volatile organic compounds. Volatile organic compounds are defined inU.S. Pat. No. 6,048,471 (Henry) and in the U.S. Federal Register: Jun.16, 1995, volume 60, number 111.

Coating compositions of the present invention preferably include areactive diluent in an amount of at least 5 weight percent (wt-%), morepreferably at least 10 wt-%, and most preferably at least 15 wt-%, basedon the combined weight of the reactive diluent and the polymer componentof the composition. Coating compositions of the present inventionpreferably include a reactive diluent in an amount of no more than 40weight percent (wt-%), more preferably no more than 30 wt-%, and mostpreferably no more than 25 wt-%, based on the combined weight of thereactive diluent and the polymer component of the composition.

Water-dispersed coating compositions of the present invention preferablyinclude at least 40 wt-% water, based on the total weight of thecomposition. Water-dispersed coating compositions of the presentinvention preferably include no more than 80 wt-% water, and morepreferably no more than 70 wt-%, based on the total weight of thecomposition.

The coating compositions of the present invention may be applied to avariety of substrates including wood, cement, tile, metal, plastic,glass, optical fibers, and fiberglass. Coating compositions can beapplied to a substrate by a variety of methods known to those skilled inthe art. Such methods include spraying, painting, rollcoating, brushing,fan coating, curtain coating, spreading, air knife coating, die-coating,vacuum coating, spin coating, electrodeposition, and dipping. Thethickness of the coatings will vary with the application. Typically, thecoatings will have a thickness of 0.1 to 20 mils (0.00025 to 0.0508centimeters (cm)), however, thicker or thinner coatings are alsocontemplated depending on, for example, the desired coating properties.

Compounds that function as reactive diluents are of relatively lowmolecular weight and can be reactive monomers, oligomers, or lowmolecular weight polymers. A compound that can function as a reactivediluent is one that can react with at least one of the polymer (thewater-dispersible polymer or oil-modified polymer), itself, anotherreactive diluent, or all of these. The polymer and reactive diluent canform, for example, an interpenetrating network. Alternatively, thereactive diluent can participate in crosslinking the polymer.

Suitable reactive diluent compounds have a relatively low molecularweight. Preferably, suitable reactive diluent compounds have a molecularweight of at least 350 grams/mole (g/mol). Preferably, the molecularweight is no more than 1000 g/mol.

Preferred reactive diluents are also substantially non-irritating, morepreferably essentially non-irritating, and most preferably completelynon-irritating. If the reactive diluent is provided as a mixture ofcompounds, the entire mixture is substantially non-irritating,preferably essentially non-irritating, and more preferably completelynon-irritating.

A “substantially non-irritating” diluent has a Draize rating of no morethan 1 for skin (on a scale of 0 to 8) and no more than 10 for eyes (ona scale of 0 to 110). An “essentially non-irritating” diluent has aDraize rating of no more than 0.5 for skin and no more than 5 for eyes.A “completely non-irritating” diluent has a Draize rating of no morethan 0.1 for skin and no more than 3 for eyes.

Preferred reactive diluents are substantially free of ethylene oxide andpropylene oxide moieties. More preferably, they are essentially free ofethylene oxide and propylene oxide moieties. Most preferably, they arecompletely free of ethylene oxide and propylene oxide moieties.“Substantially free” means that less than 5 wt-% ethylene oxide andpropylene oxide moieties are present in the reactive diluent.“Essentially free” means that less than 1 wt-% ethylene oxide andpropylene oxide moieties are present in the reactive diluent.“Completely free” means that less than 0.5 wt-% ethylene oxide andpropylene oxide moieties are present in the reactive diluent.

Preferred reactive diluents have an OH-functionality of no more than 30milliequivalents KOH/gram (meq/g). Preferably, the reactive diluent hasan OH-functionality of no more than 25 meq/g. More preferably, thereactive diluent has an OH-functionality of no more than 20 meq/g.

Reactive diluents typically include compounds with ethylenicunsaturation. Suitable such compounds include a (meth)acrylate, a vinylether, a (meth)allyl ether, or mixtures or copolymers thereof. Examplesof (meth)acrylate-functional reactive diluents includedi-trimethylolpropane tetraacrylate), di-(trimethylolpropanetetramethacrylate), di(pentaerythritol hexaacrylate),di-(pentaerythritol hexamethacrylate), pentaerythritol tetraacrylate,and pentaerythritol tetramethacrylate. Examples of vinyl ether reactivediluents include di-(trimethylolpropane tetravinyl ether),di-(pentaerythritol hexavinyl ether), and pentaerythritol tetravinylether. Examples of (meth)allyl ether reactive diluents includedi-(trimethylolpropane tetraallyl ether), di-(trimethylolpropanetetramethallyl ether), di(pentaerythritol hexaallyl ether),di-(pentaerythritol hexamethallyl ether), pentaerythritol tetraallylether, and pentaerythritol tetramethallyl ether. Preferred reactivediluent compounds are (meth)acrylate functional, which include acrylatefunctionality and methacrylate functionality. Preferred reactivediluents include (meth)acrylate functional compounds. Of these, thepreferred reactive diluent compounds are di-(trimethylolpropanetetraacrylate) and di-trimethylolpropane tetramethacrylate). Reactivediluents used in coating compositions of the present invention ifdesired can include mixtures of compounds.

Polymers suitable for the coating compositions of the present inventionare either water-dispersible or oil-modified, which can bewater-dispersible if desired. Such polymers are well-known in thecoating industry and include a wide variety of polymers.

The polymers preferably include reactive functionalities that arecapable of reacting with the aforementioned reactive diluent(s). Onesuch preferred polymer includes ethylenic unsaturation and, when cured,provides a hard, durable coating. Such ethylenic unsaturation ispreferably in the form of (meth)acrylate or auto-oxidative carbon-carbondouble bonds.

Suitable water-dispersible polymers include polyurethanes, epoxies,polyamides, chlorinated polyolefins, acrylics, oil-modified polymers,polyesters, and mixtures or copolymers thereof, for example. Suchpolymers are readily synthesized and made to be water dispersible usingconventional techniques. For example, the incorporation of amine or acidfunctionality produces water dispersibility.

Oil-modified polymers can also be used if desired, whether waterdispersible or not. As used herein, oil-modified polymers are broadlydefined to include polymers that contain oils and/or oil basedderivatives such as glyceride oils (monoglycerides, diglycerides, andthe like), fatty acids, fatty amines, and mixtures thereof. Examples ofsuch oil-modified polymers include, alkyds, oil-modified polyurethanes,oil-modified epoxies, oil-modified polyamides, oil-modified acrylics,and mixtures or copolymers thereof. Preferably, the oil-modified polymeris an oil-modified polyurethane or an alkyd. Such polymers are readilysynthesized and can be made to be water dispersible if desired usingconventional techniques.

Water-dispersible polyurethanes are particularly preferred. Thesepolymers may be made in a variety of ways. One suitable method includesreacting one or more isocyanates with one or more hydroxy-functionalcompounds. Preferred such polymers include ethylenic unsaturation aswell as salt-forming functionality. The ethylenic unsaturation can beintroduced into a polyurethane, for example, by reacting theaforementioned isocyanate with a hydroxy-functional acrylate,methacrylate, allyl ether, vinyl ether, monoglyceride, diglyceride, anester polyol, or oil-modified polymers. The preferred oil-modifiedpolymer useful in preparing an ethylenic unsaturated water-dispersiblepolyurethane is an alkyd. Preferred ethylenically unsaturatedpolyurethanes include (meth)acrylate or auto-oxidative carbon-carbondouble bond functionality.

Suitable isocyanates include diisocyanates, triisocyanates, and otherpolyisocyanates. Preferred polyisocyanates for practicing the inventionare polyisocyanates having 4 to 25 carbon atoms and from 2 to 4isocyanate groups per molecule. Examples of isocyanates are thoseconventionally used in making polyurethanes, including aliphatic,cycloaliphatic, aromatic isocyanates, and mixtures thereof.

Suitable hydroxy-functional ethylenically unsaturated compounds forreaction with the isocyanate include hydroxy-functional (meth)acrylates.Examples of suitable hydroxy-functional (meth)acrylates include alkyland cycloalkyl hydroxy-functional (meth)acrylates, such as2-hydroxyethyl (meth)acrylates, 3-hydroxypropyl (meth)acrylates,4-hydroxybutyl (meth)acrylates, 2-hydroxy-2-methylethyl (meth)acrylates,and 4-hydroxycyclohexyl (meth)acrylates, as well as other similarhydroxy-functional aliphatic (meth)acrylates. Other suitablehydroxy-functional (meth)acrylates include hydroxy-functional(meth)acrylate polyesters such as caprolactone2-((meth)acryloyloxy)ethyl esters, dicaprolactone2-((meth)acryloyloxy)ethyl esters, and higher molecular weightcaprolactone homologues, and hydroxy-functional (meth)acrylatepolyethers.

Another type of hydroxy-functional ethylenically unsaturated compoundfor use in making polyurethanes is a hydroxy-functional (meth)allylether. Suitable hydroxy-functional (meth)allyl ethers include at leastone hydroxyl group and one or more allyl ether groups, such ashydroxyethyl allyl ether, hydroxypropyl allyl ether, trimethylolpropanemonoallyl ether, trimethylolpropane diallyl ether, trimethylolethanemonoallyl ether, trimethylolpropane dimethallyl ether, and the like.

Vinyl ethers may also be utilized in making ethylenically unsaturatedpolyurethanes. A suitable vinyl ether compound includes at least onehydroxyl group and one or more vinyl ether groups. Examples of suitablevinyl ethers include 4-hydroxybutyl vinyl ether, cyclohexanedimethanolmonovinyl ether, ethylene glycol monovinyl ether, diethylene glycolmonovinyl ether, and the like.

Ethylenic unsaturation can also be incorporated into a polyurethane viareaction with an ester polyol made by reaction of an aromatic oraliphatic polyol containing at least two hydroxyl groups per moleculewith a fatty acid wherein a portion of the fatty acid containsauto-oxidative carbon-carbon double bonds. Suitable polyols includeethylene glycol, ethylene glycol, propylene glycol, 1,3 propane diol,1,3 butylene glycol, 1,4 butane diol, Bisphenol A, trimethylol propane,trimethylol ethane, pentaerythritol, glycerin, neopentyl glycol, andcyclohexane dimethanol, and mixtures thereof. Suitable unsaturated fattyacids include linoleic, palmitoleic, linolenic, eleostearic,arachidonic, ricinoleic acids, 10,12-octadecadienoic acid, and mixturesthereof.

Polyurethanes containing ethylenic unsaturation can also be developed byutilizing the reaction product formed via transesterification of an oil,containing auto-oxidative carbon-carbon double bonds, with an aromaticor aliphatic polyol containing at least two hydroxyl groups permolecule. Suitable oils include linseed oil, soybean oil, safflower oil,tall oil, sunflower oil, dehydrated caster oil, castor oil, ricine oil,tung oil, sardine oil, olive oil, cottonseed oil and mixtures thereof.Suitable polyols include ethylene glycol, propylene glycol, 1,3 propanediol, 1,3 butylene glycol, 1,4 butane diol, Bisphenol A, trimethylolpropane, trimethylol ethane, pentaerythritol, glycerin, neopentylglycol, and cyclohexane dimethanol, and mixtures thereof.

Oil-modified polymers, preferably, hydroxyl-functional alkyds can alsobe used to develop ethylenic unsaturated polyurethanes. Alkyds can beprepared by any method known in the art. An example of a method toprepare an alkyd includes the transesterification of an oil and polyolwith a further reaction with polybasic acids and optionally, furtherpolyols. In addition, polybasic acids and fatty acids can be reactedwith polyols in suitable proportions. The reaction of the polyols withpolybasic acids and fatty acids and/or oils can be catalyzed bytransesterification catalysts such as calcium naphthenate, lithiumneodecanoate, zinc acetate, tin oxide and the like. A color stabilizersuch as trisnonyl phenyl phosphite may also be added.

Suitable oils and/or fatty acids derived therefrom that are useful inmaking an alkyd or other oil-modified polymer include compounds such as,for example, linseed oil, safflower oil, tall oil, cotton seed oil,ground nut, wood oil, tung oil, ricine oil, sunflower oil, soya oil,castor oil, dehydrated castor oil, coconut oil, sardine oil, olive oil,and the like. These oils and/or fatty acids can be used alone or as amixture of one or more of the oils and/or fatty acids.

Suitable polyols useful in making an alkyd include compounds such as,for example, aliphatic, cycloaliphatic and/or araliphatic alcoholshaving 1 to 6, preferably 1 to 4, hydroxy groups attached to nonaromaticor aromatic carbon atoms, such as, for example, ethylene glycol,propylene glycol, 1,3 propane diol, 1,3 butylene glycol, 1,4 butanediol, Bisphenol A, trimethylol propane, trimethylol ethane,pentaerythritol, glycerin, neopentyl glycol, and cyclohexane dimethanol.These compounds can be used alone or as a mixture of one or morepolyols.

Suitable polybasic acids useful in making an alkyd include compoundssuch as, for example, aliphatic, cycloaliphatic saturated or unsaturatedand/or aromatic polybasic carboxylic acids, such as, for example,dicarboxylic, tricarboxylic, and tetracarboxylic acids. Polybasic acidsare broadly defined to include anhydrides of the polybasic acids suchas, for example, maleic anhydride, phthalic anhydride, succinicanhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride,trimellitic anhydride, or mixtures thereof. These compounds can be usedalone or as a mixture of one or more polybasic acids.

Alkyds can also be prepared by reacting polybasic acids with a compoundcontaining an amine to provide an amide containing alkyd. Examples ofsuitable amines include ethylene diamine, diethylene triamine,triethylene tetra amine, and melamine 1,2-diamino propane, 1,3-diaminopropane, and the like; or amino alcohols such as, for example,2-amino-propan-1-ol, 3-amino-propan-1-ol, dimethylisopropanolamine,2-amino-2-methyl-1-propanol, dimethylethanolamine, and the like. Theseamide containing alkyds can be designed to be amine and/or hydroxyfunctional and subsequently could be useful in making a waterdispersible polyurethane polymer.

Conventionally, to facilitate manufacture, the polyurethane prepolymercan be made in the presence of a solvent that is either left in thedispersion, or removed as one of the last steps in production to providea low solvent or solvent-free product. Solvents that can be easilyremoved, are usually volatile solvents, such as acetone or methyl ethylketone. In place of such solvents (or a portion of such solvents),however, one or more reactive diluents as described above are used.

Chain extenders can also be used in the preparation of urethanepolymers. Examples of chain extenders include an alkyl amino alcohol,cycloalkyl amino alcohol, heterocyclic amino alcohol, polyamine (e.g.,ethylene diamine, diethylene triamine, etc.), hydrazine, substitutedhydrazine, hydrazide, amide, water or mixtures thereof.

In general, for water dispersibility, acid salt forming groups can beintroduced into the polymer by a number of methods. For example, awater-dispersible polyurethane can be made by reacting a suitablecompound (e.g., a polyisocyanate) with a compound containing activehydrogen and active acid groups neutralized by a neutralizing base.Suitable compounds having active hydrogen and active acid groups includehydroxy and mercapto carboxylic acids, aminocarboxylic acids,aminohydroxy carboxylic acids, sulfonic acids, hydroxy sulfonic acids,and aminosulfonic acids. Suitable neutralizing bases include inorganicbases such as sodium hydroxide, potassium hydroxide, lithium hydroxide,ammonia, triethylamine, and dimethyl ethanol amine.

Alternatively, for water dispersibility, basic salt forming groups canbe introduced into the polymers by reacting a suitable compound (e.g., apolyisocyanate) with a compound containing active hydrogen groups andactive basic groups neutralized with an acid. Suitable compounds havingactive hydrogen groups and active basic groups include aliphatic,cycloaliphatic and heterocyclic amino alcohols, diols and triols,amines, diamines, triamines, tetramines, and amides. Suitableneutralizing acids include organic acids such as formic acid and aceticacid, and inorganic acids such as hydrochloric acid and sulfuric acid.

For example, urethanes can be made water-dispersible by incorporatingamine or acid functionality. For example, water-based anionicallystabilized polyurethane polymers are prepared by reacting polyols anddihydroxy carboxylic acid compounds with an excess of diisocyanate toprovide a carboxylic acid functional prepolymer having NCO terminalgroups. The acid groups can be neutralized with tertiary amines toprovide salt groups. The neutralized prepolymer can be readily dispersedin water. Alternatively, the anionic stabilizing group of thewater-dispersible polyurethane polymers can be replaced with cationicstabilizing groups or non-ionic stabilizing groups, to facilitate waterdispersibility.

Suitable additives for use in coating compositions of the presentinvention are described in Koleske et al., Paint and Coatings Industry,April, 2003, pages 12-86.

Certain embodiments of the present invention, particularly those with(meth)acrylate functional groups in the polymers and/or reactivediluents of the coating compositions, include polymers that are curableby UV or visible light. These coating compositions typically include afree-radical initiator, particularly a photoinitiator that induces thecuring reaction upon exposure to light. The photoinitiator makes upabout 0.1-10 wt-% of the coating composition.

Among photoinitiators suitable for use in the present invention withresins having (meth)acrylate or allyl ether functional groups arealpha-cleavage type photoinitiators and hydrogen abstraction typephotoinitiators. The photoinitiator may include other agents such as acoinitiator or photoinitiator synergist that aid the photochemicalinitiation reaction. Suitable cleavage type photoinitiators includealpha, alpha-diethoxyacetophenone (DEAP), dimethoxyphenylacetophenone(commercially available under the trade designation IRGACURE 651 fromCiba Corp., Ardsley, N.Y.), hydroxycyclohexylphenylketone (commerciallyavailable under the trade designation IRGACURE 184 from Ciba Corp.),2-hydroxy-2-methyl-1-phenylpropan-1-one (commercially available underthe trade designation DAROCUR 1173 from Ciba Corp.), a 25:75 blend ofbis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide and2-hydroxy-2-methyl-1-phenylpropan-1-one (commercially available underthe trade designation IRGACURE 1700 from Ciba Corp.), a 50:50 blend of2-hydroxy-2-methyl-1-phenylpropan-1-one and2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO, commerciallyavailable under the trade designation DAROCUR 4265 from Ciba Corp.),phosphine oxide, 2,4,6-trimethyl benzoyl (commercially available underthe trade name IRGACURE 819 and IRGACURE 819DW from Ciba Corp.),2,4,6-trimethylbenzoyl-diphenylphosphine oxide (commercially availableunder the trade designation LUCIRIN from BASF Corp., Mount Olive, N.J.),and a mixture of 70% oligo2-hydroxy-2-methyl-4-(1-methylvinyl)phenylpropan-1-one and 30%2-hydroxy-2-methyl-1-phenylpropan-1-one) (commercially available underthe trade designation KIP 100 from Sartomer, Exton, Pa.). Suitablehydrogen abstraction-type photoinitiators include benzophenone,substituted benzophenones (such as that commercially available under thetrade designation ESCACURE TZT from Fratelli-Lamberti, sold by Sartomer,Exton, Pa.), and other diaryl ketones such as xanthones, thioxanthones,Michler's ketone, benzil, quinones, and substituted derivatives of allof the above. Preferred photoinitiators include DAROCUR 1173, KIP 100,benzophenone, and IRGACURE 184. A particularly preferred initiatormixture is commercially available under the trade designation IRGACURE500 from Ciba Corp., which is a mixture of IRGACURE 184 andbenzophenone, in a 1:1 ratio. This is a good example of a mixture of analpha-cleavage type photoinitiator and a hydrogen abstraction-typephotoinitiator. Other mixtures of photoinitiators may also be used inthe coating compositions of the present invention. Camphorquinone is oneexample of a suitable photoinitiator for curing a coating compositionwith visible light.

A coating composition of the present invention can also include acoinitiator or photoinitiator synergist. The coinitiators can betertiary aliphatic amines (such as methyl diethanol amine and triethanolamine), aromatic amines (such as amylparadimethylaminobenzoate,2-n-butoxyethyl-4-(dimethylamino) benzoate,2-(dimethylamino)ethylbenzoate, ethyl-4-(dimethylamino)benzoate, and2-ethylhexyl-4-(dimethylamino)benzoate, (meth)acrylated amines (such asthose commercially available under the trade designations EBECRYL 7100and UVECRYL P104 and P115, all from UCB RadCure Specialties, Smyrna,Ga.), and amino-functional acrylate or methacrylate resin or oligomerblends (such as those commercially available under the tradedesignations EBECRYL 3600 or EBECRYL 3703, both from UCB RadCureSpecialties). Combinations of the above categories of compounds may alsobe used.

Coating compositions having resins with vinyl ether functional groupscan be cured by UV or visible light using cationic-generatingphotoinitiators. Examples of suitable cationic-generatingphotoinitiators include super acid-generating photoinitiators, such astriarylsulfonium salts. One useful triarylsulfonium salt is triphenylsulfonium hexafluorophosphate.

Many coating compositions that may be cured by UV or visible light mayalso be cured with an electron beam. Techniques and devices for curing acoating composition using an electron beam are known in the art. Thesetechniques do not require a photoinitiator for electron beam cure of thecoating.

Coating compositions having polymer resins with (meth)acrylate and/orallyl functional groups may also be thermally cured using a suitableinitiator. The thermal initiator typically facilitates the curingprocess by a free radical mechanism and typically includes a peroxide orazo compound. Peroxide compounds suitable for use as initiators in thecoating compositions of the present invention include t-butylperbenzoate, t-amyl perbenzoate, cumene hydroperoxide, t-amylperoctoate, methyl ethyl ketone peroxide, benzoyl peroxide,cyclohexanone peroxide, 2,4-pentanedione peroxide, di-t-butyl peroxide,t-butyl hydroperoxide, and di-(2-ethylhexyl)-peroxydicarbonate. Suitableazo compounds which may be employed as an initiator in the presentcompositions include 2,2-azo bis-(2,4-dimethylpentane-nitrile), 2,2-azobis-(2-methylbutanenitrile), and 2,2-azo bis-(2-methylpropanenitrile).

For coating compositions having a mixture of (meth)acrylate, allylether, and vinyl ether functional groups, a combination of curingprocedures may be used. For example, a coating composition having aresin with both (meth)acrylate and vinyl ether functional groupstypically includes an alpha-cleavage type and/or hydrogen abstractiontype photoinitiator for the (meth)acrylate groups and acationic-generating photoinitiator for the vinyl ether groups.

Other methods for curing the coating compositions of the invention canbe used alone or in combination with methods described hereinabove.Supplemental curing methods include heat cure, chemical cure, anaerobiccure, moisture cure, oxidative cure, and the like. Each method of curerequires a corresponding curing initiator or curing agent, which isincluded in the composition. For example: heat cure can be induced byperoxides; metal drier packages can induce an oxidative cure;multifunctional amines (for example isophorone diamine) can effect achemical crosslinking cure through Michael addition of amine groups ontoacrylate reactive unsaturated groups. If these additional initiators arepresent in the coating composition they typically make up 0.1-12% byweight of the curable coating composition. Means for effecting cures bysuch methods are known to those of skill in the art or can be determinedusing standard methods.

Certain coating compositions of the invention also can include metaldriers. Typical driers include, for example, cobalt, manganese, lead,zirconium, calcium, cerium, lanthanum, and neodymium salts orcombinations thereof. Metal driers can be used in combination withaccelerators for certain embodiments. For example, water-dispersiblepolyurethane-polyethylene compositions can also include compounds suchas, for example, 1,10-phenanthroline, bipyridine, and the like, whichfunction as accelerators in combination with the metal driers.

Certain coating compositions of the present invention may also includeone or more of a group of ingredients that can be called performanceenhancing additives. Typical performance enhancing additives that may beemployed include surface active agents, pigments, colorants, dyes,surfactants, thickeners, heat stabilizers, leveling agents,anti-cratering agents, curing indicators, plasticizers, fillers,sedimentation inhibitors, ultraviolet-light absorbers, opticalbrighteners, and the like to modify properties.

Coating compositions may include a surface-active agent that modifiesthe interaction of the curable coating composition with the substrate,in particular, the agent can modify the ability of the composition towet a substrate. Surface active agents may have other properties aswell. For example, surface active agents may also include leveling,defoaming, or flow agents, and the like. The surface active agentaffects qualities of the curable coating composition including how thecoating composition is handled, how it spreads across the surface of thesubstrate, and how it bonds to the substrate. The surface active agentmay make up 0-5% by weight of the curable coating composition.

Surface active agents suitable for use in coating compositions are knownto those of skill in the art or can be determined using standardmethods. Exemplary surface active agents include polydimethylsiloxanesurface active agents (such as those commercially available under thetrade designations SILWET L-760 and SILWET L-7622 from OSI Specialties,South Charleston, W.Va., or BYK 306 from Byk-Chemie, Wallingford, Conn.)and fluorinated surface active agents (such as that commerciallyavailable as FLUORAD FC-430 from 3M Co., St. Paul, Minn.). The surfaceactive agents may include a defoamer. Suitable defoamers includepolysiloxane defoamers (such as a methylalkylpolysiloxane like thatcommercially available under the trade designation BYK 077 or BYK 500from Byk-Chemie) or polymeric defoamers (such as that commerciallyavailable under the trade designation BYK 051 from Byk-Chemie).

For some applications, a coating that is opaque, colored, pigmented orhas other visual characteristics is desired. Agents to provide suchproperties can also be included in coating compositions of the presentinvention. Pigments for use with the present invention are known in theart. Suitable pigments include titanium dioxide white, carbon black,lampblack, black iron oxide, red iron oxide, yellow iron oxide, browniron oxide (a blend of red and yellow oxide with black), phthalocyaninegreen, phthalocyanine blue, organic reds (such as naphthol red,quinacridone red and toulidine red), quinacridone magenta, quinacridoneviolet, DNA orange, and/or organic yellows (such as Hansa yellow). Thecomposition can also include a gloss control additive or an opticalbrightener, such as that commercially available under the tradedesignation UVITEX OB from Ciba-Geigy.

In certain embodiments it is advantageous to include fillers or inertingredients in the coating composition. Fillers and inert ingredientsinclude, for example, clay, glass beads, calcium carbonate, talc,silicas, organic fillers, and the like. Fillers extend, lower the costof, alter the appearance of, or provide desirable characteristics to thecomposition before and after curing. Suitable fillers are known to thoseof skill in the art or can be determined using standard methods. Fillersor inert ingredients can make up from 0.1-40% by weight of the coatingcomposition.

The invention may also include other ingredients that modify propertiesof the curable coating composition as it is stored, handled, or applied,and at other or subsequent stages. Waxes, flatting agents, mar andabrasion additives, and other similar performance enhancing additivesmay be employed in this invention as required in amounts effective toupgrade the performance of the cured coating and the coatingcomposition. Desirable performance characteristics of the coatinginclude chemical resistance, abrasion resistance, hardness, gloss,reflectivity, appearance, or combinations of these characteristics, andother similar characteristics.

EXAMPLES

Objects and advantages of this invention are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention.

The following abbreviations have been used herein:

-   -   DMPA—Dimethylolpropionic acid (GEO, Allentown, Pa.)    -   DiTMPTA—Di-trimethylolpropane tetraacrylate (Sartomer, Exton,        Pa.)    -   4-HBA—4-Hydroxy butylacrylate (Aldrich, Milwaukee, Wis.)    -   TMP—Trimethylol Propane (Aldrich)    -   DESMOPHEN S-105-110—Polyester diol (Bayer, Pittsburgh, Pa.)    -   TEA—Triethyl Amine (Aldrich)    -   DBTDL—Dibutyl Tin Dilaurate (Air Products, Allentown, Pa.)

Example 1 Preparation of (meth)acrylate Functional PolyurethaneDispersion (PUD) with DiTMPTA Reactive Diluent

A reactor was charged with 96.0 parts DiTMPTA, 48.0 parts 4-HBA, 91.4parts DESMOPHEN S-105-110 polyester diol, 29.3 parts DMPA, 9.6 partsTMP, an amount of a diisocyanate, and 500 ppm of 2,6di-tert-butyl-4-methylphenol. The reaction mixture was heated to 80° C.under an air sparge, where upon 250 ppm DBTDL was added and the reactionprocessed until the isocyanate level was below 9.2%. The urethanepolymer was cooled to 65° C. and then neutralized with 22.1 parts TEA.The urethane polymer viscosity at 65° C. was 6,000 centipoise (cps) asmeasured by a Brookfield DV-I+ Viscometer and a Number 31 spindle at 1.5revolutions per minute (RPM).

At a process temperature of 65° C., the (meth)acrylate urethane polymerformed above was then dispersed into 895.5 parts room temperaturedeionized water and subsequently chain extended with 51.1 partshydrazine (35% in water). The dispersion was then adjusted to 35% solidswith deionized water.

The physical properties of the chain extended (meth)acrylate functionalpolyurethane dispersion were as follows (NVM %=nonvolatile material byweight):

EXAMPLE 1 NVM %  35% % VOC 1.4% (TEA)

Example 2 UV Curable Coating Composition with DiTMPTA Containing(meth)acrylate Functional PUD

Under agitation to a stainless steel mixing vessel was added 85 parts ofthe dispersion from Example 1, 0.85 part, IRGACURE 500 from Ciba, 8.05parts deionized water, 5.00 parts DOWANOL DPM from Dow Chemical, 1.00part SURFYNOL 104PA from Air Products, and 0.10 part BYK 333 from BYKChemie. A 3-mil thick (0.00762-cm) wet film was then applied to a LenetaForm 7B test chart and air dried for 15 minutes followed by force dryfor 5 minutes at 65° C. The dried (meth)acrylate polymer film was thencured by mercury ultraviolet lamps. Total UV exposure was 1000millijoules per square centimeter (mj/cm²).

Performance properties are outlined below. Gloss is reported inaccordance with ASTM test specification, D-523. All other cured filmproperties are reported on a scale of 1-10, with 10 being no effect orbest.

TEST RESULT Gloss 60 degree measurement 88-90 1 hour Exposure to mustard   9+ 1 hour exposure to 100 proof  9 vodka 100 MEK double rubs  9 180degree flexibility 10 Fingernail mar 10

Gloss measurement was performed with a Micro-Gloss 60 from BYK Gardnerin accordance with ASTM test method D-523.

1-Hour spot test exposure to 100 proof vodka and to mustard wereperformed in accordance with ASTM test method D-1308.

MEK double rub testing was performed in accordance with ASTM test methodD-5402.

180-Degree flexibility was performed by bending the test chart 180degrees around a ½ inch (1.27 cm) diameter rod and visually looking forfilm cracking.

Fingernail mar was performed by rubbing the back of the fingernailsoftly across the cured coating and looking for surface mar.

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

1. A method of preparing a coating composition, the method comprising:providing a mixture comprising a water-dispersible polymer and areactive diluent, wherein the water-dispersible polymer is prepared inthe presence of the reactive diluent, wherein the mixture has aviscosity below 100,000 centipoise at processing temperatures, andfurther wherein the reactive diluent is present in an amount of 5 wt-%to 40 wt-%, based on the total weight of the reactive diluent and thewater-dispersible polymer, and includes a compound having a molecularweight of 350 grams/mole to 1000 grams/mole and, is substantially freeof ethylene oxide and propylene oxide moieties and has anOH-functionality of no more than 30 milliequivalents KOH/gram, with theproviso that the reactive diluent does not include pentaerythritoltetraacrylate; and dispersing the mixture in water.
 2. The method ofclaim 1 wherein the water-dispersible polymer is selected from the groupconsisting of polyurethanes, epoxies, polyamides, chlorinatedpolyolefins, acrylics, oil-modified polymers, polyesters, and mixturesor copolymers thereof.
 3. The method of claim 2 wherein thewater-dispersible polymer is a water-dispersible polyurethane.
 4. Themethod of claim 3 wherein the water-dispersible polyurethane comprisesamine or acid functionality.
 5. The method of claim 3 wherein thewater-dispersible polyurethane comprises ethylenic unsaturation.
 6. Themethod of claim 5 wherein the ethylenic unsaturation comprises(meth)acrylate functionality.
 7. The method of claim 5 wherein theethylenic unsaturation comprises auto-oxidative carbon-carbon doublebonds.
 8. The method of claim 1 wherein the coating composition furthercomprises a metal drier.
 9. The method of claim 1 wherein the coatingcomposition further comprises a free-radical initiator.
 10. The methodof claim 1 wherein the coating composition comprises no more than 7 wt-%volatile organic compounds.
 11. The method of claim 1 wherein thereactive diluent comprises a compound selected from the group ofdi-(trimethylolpropane tetraacrylate), di-(trimethylolpropanetetramethacrylate), di-(pentaerythritol hexamethacrylate),dipentaerythritol hexaacrylate, pentaerythritol tetramethacrylate,di-(trimethylolpropane tetravinyl ether), di-(pentaerythritol hexavinylether), pentaerythritol tetravinyl ether, di-(trimethylolpropanetetraallyl ether), di-(trimethylolpropane tetramethallyl ether),di(pentaerythritol hexaallyl ether), di-(pentaerythritol hexamethallylether), pentaerythritol tetraallyl ether, pentaerythritol tetramethallylether, and mixtures thereof.
 12. The method of claim 1 wherein thereactive diluent comprises a compound selected from the group consistingof di-(trimethylolpropane tetraacrylate), di-(trimethylolpropanetetramethacrylate), and combinations thereof.
 13. The method of claim 1wherein the reactive diluent comprises a (meth)acrylate, a vinyl ether,a (meth)allyl ether, or mixtures or copolymers thereof.
 14. The methodof claim 13 wherein the reactive diluent comprises a(meth)acrylate-functional compound.
 15. The method of claim 14 whereinthe (meth)acrylate-functional compound is selected from the groupconsisting of di-(trimethylolpropane tetraacrylate),di-(trimethylolpropane tetramethacrylate), and combinations thereof. 16.The method of claim 1 wherein the reactive diluent is present in anamount of 10 wt-% to 30 wt-%, based on the total weight of the reactivediluent and the water-dispersible polymer.
 17. The method of claim 1,wherein the water-dispersible polymer is an oil-modifiedwater-dispersible polymer.
 18. The method of claim 17 wherein theoil-modified water-dispersible polymer is an alkyd.
 19. The method ofclaim 17 wherein the oil-modified water-dispersible polymer is anoil-modified water-dispersible polyurethane.
 20. The method of claim 19wherein the reactive diluent is present in an amount of 10 wt-% to 30wt-%, based on the total weight of the reactive diluent and theoil-modified water-dispersible polymer.
 21. The method of claim 19wherein the reactive diluent comprises a (meth)acrylate, a vinyl ether,a (meth)allyl ether, or mixtures or copolymers thereof.
 22. The methodof claim 21 wherein the reactive diluent comprises a(meth)acrylate-functional compound.
 23. The method of claim 22 whereinthe (meth)acrylate-functional compound is selected from the groupconsisting of di-(trimethylolpropane tetraacrylate),di-(trimethylolpropane tetramethacrylate), and combinations thereof. 24.The method of claim 17 wherein the reactive diluent comprises a compoundselected from the group of di-(trimethylolpropane tetraacrylate),di-(trimethylolpropane tetramethacrylate), di-(pentaerythritolhexamethacrylate), pentaerythritol tetramethacrylate,di-(trimethylolpropane tetravinyl ether), di-(pentaerythritol hexavinylether), pentaerythritol tetravinyl ether, di-(trimethylolpropanetetraallyl ether), di-(trimethylolpropane tetramethallyl ether),di(pentaerythritol hexaallyl ether), di-(pentaerythritol hexamethallylether), pentaerythritol tetraallyl ether, pentaerythritol tetramethallylether, and mixtures thereof.
 25. The method of claim 24 wherein theoil-modified water-dispersible polymer is an alkyd.
 26. The method ofclaim 24 wherein the mixture comprises no more than 7 wt-% volatileorganic compounds.
 27. The method of claim 24 wherein the reactivediluent comprises a compound selected from the group consisting ofdi-(trimethylolpropane tetraacrylate), di-(trimethylolpropanetetramethacrylate), and combinations thereof.
 28. The method of claim 24wherein the mixture further comprises a metal drier.
 29. The method ofclaim 24 wherein the reactive diluent comprises a compound selected fromthe group of di-(trimethylolpropane tetraacrylate),di-(trimethylolpropane tetramethacrylate), pentaerythritoltetramethacrylate, di-(trimethylolpropane tetravinyl ether),di-(pentaerythritol hexavinyl ether), pentaerythritol tetravinyl ether,di-(trimethylolpropane tetraallyl ether), di-(trimethylolpropanetetramethallyl ether), di(pentaerythritol hexaallyl ether),di-(pentaerythritol hexamethallyl ether), pentaerythritol tetraallylether, pentaerythritol tetramethallyl ether, and mixtures thereof. 30.The method of claim 29 wherein the mixture further comprises a metaldrier.
 31. The method of claim 29 wherein the oil-modifiedwater-dispersible polymer is an alkyd.
 32. The method of claim 1 whereinif the reactive diluent is provided as a mixture of compounds, theentire mixture is substantially non-irritating.
 33. The method of claim1 wherein the water-dispersible polymer comprises an acid forming group,and wherein the method further comprises neutralizing the acid forminggroup with a neutralizing base prior to dispersing the mixture in water.34. The method of claim 1 wherein the water-dispersible polymercomprises a urethane polymer, and wherein the method further comprisesproviding chain extenders to the mixture after dispersing the mixture inwater.
 35. A method of preparing a coating composition, the methodcomprising: providing a mixture comprising a water-dispersible polymerand a reactive diluent, wherein the water-dispersible polymer isprepared in the presence of the reactive diluent, wherein the mixturehas a viscosity below 100,000 centipoise at processing temperatures, andfurther wherein the reactive diluent is present in an amount of 5 wt-%to 40 wt-%, based on the total weight of the reactive diluent and thewater-dispersible polymer, wherein the reactive diluent is substantiallynon-irritating; and wherein if the reactive diluent is provided as amixture of compounds, the entire mixture is substantiallynon-irritating; and dispersing the mixture in water.
 36. The method ofclaim 35 wherein the reactive diluent is present in an amount of 10 wt-%to 30 wt-%, based on the total weight of the reactive diluent and thewater-dispersible polymer.
 37. The method of claim 35 wherein themixture comprises no more than 7 wt-% volatile organic compounds. 38.The method of claim 35 wherein the water-dispersible polymer comprises a(meth)acrylate-functional water-dispersible polyurethane, and thesubstantially non-irritating reactive diluent comprises a(meth)acrylate-functional compound.
 39. The method of claim 38 whereinthe (meth)acrylate-functional compound is selected from the groupconsisting of di-(trimethylolpropane tetraacrylate),di-(trimethylolpropane tetramethacrylate), and combinations thereof. 40.The method of claim 35 wherein the water-dispersible polymer comprisesan oil-modified water-dispersible polyurethane, and the substantiallynon-irritating reactive diluent comprises a (meth)acrylate-functionalcompound.
 41. The method of claim 40 wherein the(meth)acrylate-functional compound is selected from the group consistingof di-(trimethylolpropane tetraacrylate), di-(trimethylolpropanetetramethacrylate), and combinations thereof.
 42. The method of claim 40wherein the mixture further comprises a metal drier.
 43. The method ofclaim 35 wherein the reactive diluent does not include pentaerythritoltetraacrylate.
 44. The method of claim 35 wherein the water-dispersiblepolymer comprises an acid forming group, and wherein the method furthercomprises neutralizing the acid forming group with a neutralizing baseprior to dispersing the mixture in water.
 45. The method of claim 35wherein the water-dispersible polymer comprises a urethane polymer, andwherein the method further comprises providing chain extenders to themixture after dispersing the mixture in water.